Nickel steel alloys



Patented Nov. 28, 1950 Harold D. Newell, Beaver Falls, -Pa., assignor toThe Baboock & Wilcox Tube Company, West Mayiield, Pa., a corporation ofPennsylvania No Drawing. Application September 17, 1946,- Serial No.697,5"l

Claims. (01. -125 This invention relates to improved nickel alloy steelcompositions and more particularly to nickel alloy steels resistant tocertain corroding influences and having good toughness characteristicswith ductility and resistance to impact at sub-zero temperatures.

Heretofore, it has been customary to use nickel steels for machineparts, for automotive parts, for carburized roller bearings and forother purposes in the usual form of SAE or NE grades with nickelcontents up to 5% or thereabouts. Steels with up to this amount ofnickel are also combined with small quantities of chromium, molybdenum,vanadium, silicon or other alloying ingredients, and the carbon contentis adjusted to suit the end use or requirement for hardness, strength orother properties. High nickel steel alloys containing 30% or more nickelare also well known and have been used for their special properties ofelectrical resistance, low expansion rates or other features. Commercialsteels, exclusive of stainless steels, have not been made and usedcontaining more than about 5.25 per cent nickel and-this is especiallyso of steels containing between about 7 per cent and 12 per cent nickelbecause such steels are hard and martensitic in character and lackductility and are difllcult to anneal so as to soften them formachining, expanding, bending or other forming operations. Consequently,such steels have previously not been available in tubing or pipe orother articles as they were considered to be laboratory curiosities notusable commercially because of their peculiar properties.

. The present invention makes available nickel in welded constructionsby the use of well-known welding methods if certain practices arefollowed as to preheating and postheating the metal following thewelding operations.

The main object of the present invention is to provide a new seriesoinickel alloy steels which may be varied as to composition to providevarious properties of corrosion resistance to atmosphere, to alkalinesolutions or mild organic acid conditions (pH 2.0 to 6.0), to chlorideand sulphide solutions, or other forms of corrosion where presentlyavailable lower alloy content steels, including the commercial nickelsteels,

' are not adequate or economical because of their lack of corrosionresistance or unsuitable physical properties for special fields ofservice. Another and more specific object is to' provide for themanufacture of articles requiring steels having toughnessv and ductilitysuch as tubes, pipe, rods, containers, valves and fittings, and otherformed appurtenances for industrial use as in 0115111 use.

The new series of nickel alloy steels made in accordance with thepresent invention have in general the following composition:

Per cent Carbon 0.03to 0.20 Manganese 0.20 to 1.00 Silicon 0.03to 0.40Nickel 7.50 to 12.00 Chromium 0.02to 6.00 Copper 0z.05:t0 $00 Molybdenum0.03to 2.00

Titanium, columbium, zirconium or vanadium singly or in combination 0.0to 1.00 with the balance substantially all iron.

a 3 ingots, blooms, bars or, tubes should be low in sulphur for bestresults.

The steels should be thoroughly deoxfdized, usually with one to twopounds or more of aluminum per ton to produce steels with fine grainedcharacteristics having high toughness and ductility. This is necessaryfor retention of impactstrength at low temperature and such thoroughdeoxidation has the further advantage of stimulating reaction ratesduring annealing and reducing strain-aging properties. Silicon ispreferably kept below 0.25 per cent and the steels should be poured intohot-topped molds.

With respect to composition, the nickel content, although not limitedthereto, is usually ranged between a and per cent in a low carbon base,the carbon being restricted in most cases to 0.12 per cent maximum and,where maximum ductility and softness is required in the finishedproduct, as in tubes for bending or ex-- carbon is limited to .20 percent maximum, or more often is restricted to .12 per cent or less, thehardenability of the steel is reduced and the working, annealing andmachining of these nickel steels is greatly improved. However, tofurther reduce hardenability and to provide easy workability, goodductility and ease of annealing, such as necessary in the manufacture ofductile seamless tubes suitable for expanded Joints or bends,

panding, the carbon should be under 0.10 per cent, i. e. about 0.06 to0.09 per cent. Even lower carbon may be advantageous in certaincircumstances to avoid formation of a hard martensitelike constituentwhich has heretofore been characteristic of alloy steels having a nickelcontent I have found it desirable to incorporate one or more strongcarbide formers to tie up carbon and render it ineifectlv'e in formingand retaining the hard and brittle martensite-like constituent.

This is accomplished by adding titanium up to the eyuivalent of four ormore times the carbon content. -When columbium is added up to ten timesthe carbon content, it has an equal eifect in suppressing hardenability.Zirconium and/or vanadium may also be used for their effects of thiskind. For this purpose, zirconium may be added in a ratio up to 8-10times the carbon content and vanadium up to 4 or more times the carboncontent, depending on whether it is in the range disclosed. Copper isusually added to the composition for "its beneficial efl'ect in creatingbetter corrosion resistance toward the atmosphere and other corrosivemedia including alkalies and mild acids. The usual addition is 0.20 to0.40 per cent copper. Where high ultimate strengths are required thecopper ,may be raised to 1.00 per cent or more and this adds further tothe corrosion resistant properties of the alloys, at the same timepermitting agehardening reactions to occur in the steel upon temperingtreatments, with decided improvement in physical properties. In fact,carbon can be kept very low in my allow steels, and copper may be usedto strengthen them by precipitation hardening on applying appropriateheat treatments. Such heat treatments consist of normalizing orquenching from above the A3 point and thereafter tempering between about850 F and 1100 F.

Molybdenum may be added as required to the extent of upwards of 2.00 percent to benefit corrosion resistance particularly under mild acidcorrosion conditions. When used, a preferred amount is approximately0.50 per cent molybdenum. Chromium, when added to my nickel steels, isused for improvement of corrosion resistance. It also alters physicalproperties. Approximately 5 per cent chromium may be added although alesser amount has a beneficial effect. For resist-' ance to alkalies orfor good toughness at low temperature, chromium is not required and isnot incorporated in my preferred alloy.

Manganese is incorporated as in good alloy steel practice and may bepresent between about 0.20 and 1.00per cent. About 0.30/0.60 per cent isthe usual addition. Phosphorus is generally low and for maximumsoftness, silicon can be ranged near the low limit or about 0.20-0.05per cent.

The usual nickel alloy steels having a nickel content of about 5.0 to12.0 per cent or more tend to be hard and brittle due to thecharacteristic formation of a martensite-like constituent which isdifficult to break down to ferrite and carbides even on extendedannealing. cycles. When the alloying constituents previously describedare combined in the proportions disclosed, and the desired to fairlyfully suppress or only partially suppress hardening reactions. Thesecarbide forming elements may be used singly or together corporated inthe steels upto a total of not exceeding 1.00 per cent construed ascoming within the scope of the invention. The titanium, vanadium,columbium and/or zirconium may be added in the form of the usualferro-alloys as metals, or special deoxidizers or reduced into the metalfrom their oxides or, other compounds. Titanium is the preferredaddition because of the low ratio required for carbide formation andbecause it is most economical. Other advantages accrue from using thesecarbide formers in my alloys as they tend to suppress causticembrittlement and they reduce strain-aging effects in the metal.

As is disclosed, several'variations of my alloy may be used dependingupon exact use. My preferred range for general use is:

with the balance substantially all iron.

Typical heats of this nickel steel alloy made for use as tubes in alkalievaporators had analyses and grain sizes as follows:

TableI McQuaidgfij 0 Mn Si 01' Ni Cu Mo Ehn Grain Size pering, afternormalizing, the impact strengths improved greatly as may also be notedin the same table.

. s Table Ila-impact properties Standard Charpy specimen .394" spare-drilled ke hole notch. Values shown are average of three spec mensof each eat at'each temperature. All tests made on specimens takenlongitudinal to rolling direction. I

Other alloys coming within the scope of the invention are disclosed asto composition in Table III. Usual heat treatments applied consist ofnormalizing at about 1575 F., or double normalizing and tempering atabout 1050 F. ,Witl'. selection of composition and treatment, wide rangeof physical properties may be provided. Typical properties obtained onmy alloys in these circumstances may be noted in Table IV. In surveyingthese values, it may be noted that titanium additions are useful forsoftening and reduction of silicon content is also helpful toward thatend where maximum ductility might be required in the article.

Theiareferred double normalizing heat treatment consists in firstnormalizing at a temperature of approximately 1625 F. and a secondnormalizing at a temperature of approximately 1450 F.

Table IIL-Chemical analysis Using the compositions set forth, I am ableto provide corrosion resistance in a variety of media which exceeds thatavailable in the usual structural nickel steels, particular-advantagebeing securedwhen articles of my alloys are exposed to alkaline media.Good resistance is also secured under mildly acidic conditions.

Physical properties may be altered in my steels by variation within therange of composition set forth to obtain high strength with reasonableductility, or softer more ductile material may be provided as required.Mypreferred alloy composition offers high impact strength and retainsits toughness to much lower temperatures than any of the lesser alloycontent engineering steels and consequently may be employed to replacestainlss austenitic steels or non-ferrous metals in equipment intendedfor sub-zero service. It is especially useful when service temperaturesfall below about minus 1'75 F.

My alloys may be rolled -or manufactured into useful industrial articlessuch as tubing and pipe for conveying fluids, into sucker rods, valveparts, oil well appurtenances, bearings for carburizing and into otherarticles as desired. Ordinary equipment usually available in steel millsmay be used to convert the metal from ingot to other wroughtforms. Myalloy steels can be substituted for steels having lesser corrosionresistance or inferior physical properties at moderate increase in costover those presently available commercially and at much lower cost thanfor the high chromium-nickel stainless steels.

The analyses given in Table III are illustrative and the objects of thepresent invention may be realized by altering the composition within theranges set forth in the claims made hereinafter.

I claim:

Alloy I o I Mn I s1 I Ni 011 Mo v Ti Cr 40 1. A forgeable and machinablealloy steel characterized by high resistance to alkali and ,mild 0.120.05 0.15 3.01 0.05 0 m 0.50 acidic corrosion, said steel having thefolio 31% 3120 8153 01% 0.55 composition 4 .21 9.32 0.38 3.53 3.34 8.509.21 0.22 from 0.03 to 0.20% carbon M0 M3 from 0.20 to 1.00% manganese0.08 0.45 0.20 9.50 0.81 0.58 5.50 0.10 0.00 0.38 9.40 0. 48 0.5a 0.215.53 from 0. 2 to 0. 0% silicon 906 M7 from 7.50 to 12.00% nickel from0.20 to 2.00% copper Table IV .---Physical properties Elong. 11011.01Ultimate Yield Impact Allo Condition 1 Per Cent Area. BHN Y p. s. 1. p.s. 1. m Ft. Lbs.

Normalized 185,750 151,000 13.0 47.2 307 18.5 .50 C1- 7 DoubleNormalized 191, 200 159, 250 11.5 44. 4 408 18. 5 Double Normalized andTempered.. 1 250 117, 750 20. 0 60. 1 285 32. 5 Normalized 139, 000 113,000 15. 0 55.5 287 25. 0 .20 Mo 8 {Double Normalized" 131, 000 108, 80015.0 49. 9 309 27. 0 Double Normalized and Tempered 120, 750 109, 15020. 0 57. 7, 265 36. 5 Normalized 147,000 125, 100 15.5 I 57.3 305 9Double Normalized; 500 110, 500 17. 0 58. 4 278 25. 0 Double Normalizedand Tempered- 106, 300 90, 250 22. 0 65. 8 230 41. 0 Normalized 135, 200115, 000 17. 0 59. 6 305 26. 5 10 {Double Normalized 122, 500 102, 00019. 0 07. 3 263 37. 0 Double Normalized an 122, 800 109, 000 20.0 67. 4275 41. 0 orm zed 104, 750 83,600 24.0 67.9 229 53.5 11 {DoubleNormalized 108, 000 81, 250 26. 0 67. 8 228 54. 5 Double Normalized andTempered- 90, 000 79, 750 26. 0 68. 2 227 56.5 Normalized 142, 400 118,900 15.0 54.4 307 22. 0 12 {Double Normalized 137,000 114, 200 26. 0 45.8 293 20. 5 Double Normalized and empered-- 133,000 1 500 18.0 51. 5 30033. 0 Normalized 180,500 147, 050 15.0 53.7 387 21.5 13 {DoubleNormalized 192,000 153, 500 12. 0 47.0 427 15.0 Double Normalized andTempered 152, 250 142, 000 18.0 59. 4 342 21. 5 Normalized 107,000158,000 13.5 50.8 301 14 Double Normalized 202, 500 154, 300 12. 5 44. 2385 26.5 Double Normalized and Tempered 167, 200 105, 500 13. 0 51.2 30343. 0 Normalized -1 144, 000 119, 750 15. 0 53. 3 312 18. 0 15 DoubleNormalized 138, 800 119, 300 17. 0 58. 9 299 21. 5 Double Normalized andTempered... 137,1110 124, 800 21. 0 01. 2 303 31. 5

. incidental impurities.

\ balance iron and incidental impurities.

up to 8.00% chromium up to 2.00% molybdenum and up to 1.00% of a carbideformer selected from the group consisting of titanium, columbium,zirconium and vanadium; balance iron and 2. A iorgeable and machinablealloy steel characterized by hi h resistance to alkali and mild acidiccorrosion, said steel having the 101 lowing composition up to 0.12%carbon from 0.40 to 0.60% manganese from 8.00 to 10.00% nickel from 0.05to 0.25% silicon from 0.20 to 2.00% copper balance iron and incidentalimpurities 3. A iorgeable and machinable alloy steel characterized byhigh resistance to'alkali and mild acidic corrosion, said steel havingthe following composition from 0.06'to 0.09% carbon from 0.40 to 0.50%manganese from 8.80 to 9.20% nickel from 0.15 .to 0.25% silicon from0.20 to 0.40% copper from 0.03 to 0.11% chromium from 0.04 to 0.07%molybdenum 4. A torgeable and machinable alloy steel characterized byhigh resistance to alkali and mild acidic corrosion, said steel havingtheiollowing composition up to 0.12% carbon from 0.30 to 0.60% manganesefrom 8.00 to 10.00% nickel up to 0.25% silicon from 0.20 to 0.40% copperup to 0.50% molybdenum and titanium up to 4 times the carbon content;balance iron and incidental impurities.

5. A nickel steel alloy tubular article composed of the alloy steeldefined in claim 1; said article having been normalized and tempered.

' HAROLD D. NEWELL.

REFERENCES crrnn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. A FORGEABLE AND MACHINABLE ALLOY STEEL CHARACTERIZED BY HIGHRESISTANCE TO ALKALI AND MILD ACIDIC CORROSION, SAID STEEL HAVING THEFOLLOWING COMPOSITION